FUTURE RESEARCH PLANS: 1. The results of experiments analysed at present should tell us what is the minimum number of microtubules and their spacial arrangement in the spindle which still permits functional ability (except the rate) to move chromosomes. We will attempt to find conditions when such spindle structure is retained after lysis (temperature, glycols, and correct lysing solutions). We plan to do most experiments on tissue cultures of the newt -- the technique which has been recently spectacularly improved in my laboratory. Following the behavior of single microtubule in the light microscope (technique being perfected now) opens new possibilities and approaches to the model system in vitro. Lysing and isolation procedure of individual spindles will be monitored in the light microscope (control EM), using this technique. Monitoring of changes resulting from addition of procine tubuline should permit us to make preliminary evaluation of the model system in vitro. 2) Experiments on microtubules disassembly and lateral interaction (combined with hexylene glycol) in vivo are planned and already partly started. We will try to "unzip" kinetochore fibres of experimentally obtained lagging chromosomes and monitor their behavor in light and electron microscope. 3. Preliminary experiments on whitefish embryos are planned. We hope that a few weeks next year will permit us to evaluate potential of this totally new material for studies on cell division. We hope that this material will be especially suitable in answering some questions outlined in the original proposal. BIBLIOGRAPHIC REFERENCES: Mechanism of chromosome movements and interaction of microtubules. (A. Bajer, J. Mole-Bajer and A.M. Lambert). Microtubules and microtubule inhibitors edt.: M. Borgers and M. de Brabander 1975: 393-423 Elsevier, Holland. Dynamics of prometaphase and fine structure of the spindle. (A.M.Lambert and A. Bajer). J. Micr. Biol. Cell. Paris, France (1975) 23, 181-194.